The present invention relates to photothermographic materials exhibiting superior transport property in processing in an automatic processor, reduced fogging and improved stability in variation of processing conditions, and an image forming process by use thereof.
In the field of printing plate-making and medical diagnosis, waste liquor produced in wet-processing of image forming material comes into problems and reduction of processing effluent is strongly desired in terms of environmental protection and space saving. Accordingly, a technique for photothermographic materials is required, which enables efficient exposure by means of a laser image setter or a laser imager and formation of black images exhibiting high resolution and clearness.
As such a technique is known a thermally developable photothermographic material which comprises on a support an organic silver salt, light sensitive silver halide grains, reducing agent and a binder, as described in U.S. Pat. Nos. 3,152,904 and 3,487,075, and D. Morgan xe2x80x9cDry Silver Photographic Materialsxe2x80x9d in Handbook of Imaging materials page 48 (Marcel Dekker Inc., 1991).
Photothermographic materials are usually processed by an automatic processor and processing at a temperature higher than 105xc2x0 C. easily cause deformation of material, producing problems in transport. Specifically, problems arise in photothermographic materials in which polymeric latexes disclosed in JP-A 10-186568 are employed as a binder (hereinafter, the term, JP-A refers to an unexamined, published Japanese Patent Application). JP-A 9-297369 discloses a technique of a photothermographic material having a lowered Beck flatness. To achieve this, however, a relatively large amount of a large-sized matting agent need to be incorporated. Such a photothermographic material was inferior in haze, producing problems that the exposure time markedly increased at the time of printing onto a pre-sensitized plate for use in plate-making and reproducibility of small dots was deteriorated, and therefore was not put into practical use.
Further, since photothermographic materials need not be subjected to a fixing treatment, there is a problem such as an aging increase of fog density. Another problem also arose such that photographic performance was deteriorated when the processing conditions were varied, specifically when the developing temperature was lowered. U.S. Pat. Nos. 5,545,515 and 5,545,505 disclose the use of a contrast-increasing agent in photothermographic materials. However, it was proved that the use of such a contrast-increasing agent resulted in deteriorated photographic performance when the developing temperature was lowered. JP-A 10-69023 teaches a photothermographic material containing a polymeric latex as binder, however, deterioration of photographic performance caused by a lowering of the developing temperature was not improved.
As can be seen from the foregoing, improvements in transport property, fogging after development and stability in variation of the processing conditions are desired in photothermographic materials.
It is an object of the present invention to provide a photothermographic material improved in transport property in processing in an automatic processor, fogging after being processed and stability in variation of processing conditions, and an image forming process by use thereof.
The object of the present invention can be accomplished by the following constitution:
1. A photothermographic material comprising a support, silver halide, an organic silver salt and a reducing agent, wherein the photothermographic material meets the following requirement:
xe2x88x9215 less than 100xc3x97(S1-S0)/S0 less than 15
wherein S0 represents a sensitivity of the photothermographic material heat-developed after being allowed to stand at 23xc2x0 C. and 50% RH for a period of 3 days and S1 represents a sensitivity of the photothermographic material heat-developed after being allowed to stand at 55xc2x0 C. and 80% RH for a period of 3 days, provided that the sensitivity is represented by the logarithm of a reciprocal of exposure giving a density of 2.5 obtained when the photothermographic material is exposed and heat-developed at 117xc2x0 C. for 20 sec.;
2. The photothermographic material described in 1., wherein the photothermographic material comprises on the support component layers including an image forming layer, the image forming layer comprising the organic silver salt and the silver halide, and the image forming layer or a component layer adjacent to the image forming layer comprising the reducing agent;
3. The photothermographic material described in 2., wherein the image forming layer or a component layer adjacent to the image forming layer comprises a contrast-increasing agent;
4. The photothermographic material described in 1., wherein the photothermographic material exhibits an equilibrium moisture content of not more than 2% by weight;
5. The photothermographic material described in 2., wherein the uppermost layer of the image forming layer comprises a binder, the binder exhibiting an equilibrium moisture content of not more than 2% by weight;
6. The photothermographic material described in 2., wherein the photothermographic material exhibits a Vickers hardness of 40 to 150 on the image forming layer-side;
7. The photothermographic material described in 1., wherein the reducing agent is incorporated in the form of a solid particle dispersion;
8. The photothermographic material described in 1., wherein the photothermographic further comprises a tone modifier in the form of a solid particle dispersion;
9. The photothermographic material described in 1., wherein the silver halide is monodisperse grains;
10. The photothermographic material described in 1., wherein the organic silver salt is monodisperse grains having an average size of not more than 2 xcexcm;
11. A method for processing a photothermographic material comprising:
subjecting the photothermographic material to heat-development,
wherein the photothermographic material is subjected to heat-development at a temperature of 105 to 145xc2x0 C.; and the photothermographic material comprises a support, silver halide, an organic silver salt and a reducing agent, and meeting the following requirement (1):
xe2x88x9215 less than 100xc3x97(S1-S0)/S0 less than 15xe2x80x83xe2x80x83requirement (1)
wherein S0 represents a sensitivity of the photothermographic material heat-developed after being allowed to stand at 23xc2x0 C. and 50% RH for a period of 3 days and S1 represents a sensitivity of the photothermographic material heat-developed after being allowed to stand at 55xc2x0 C. and 80% RH for a period of 3 days, provided that the sensitivity is represented by the logarithm of reciprocal of exposure giving a density of 2.5 obtained when the photothermographic material is exposed and heat-developed at 117xc2x0 C. for 20 sec.;
12. An exposure method of a photothermographic material comprising:
exposing the photothermographic material to light, wherein the photothermographic material comprises a support, silver halide, an organic silver salt and a reducing agent, and meeting the following requirement (1):
xe2x88x9215 less than 100xc3x97(S1-S0)/S0 less than 15xe2x80x83xe2x80x83requirement (1)
wherein S0 represents a sensitivity of the photothermographic material heat-developed after being allowed to stand at 23xc2x0 C. and 50% RH for a period of 3 days and S1 represents a sensitivity of the photothermographic material heat-developed after being allowed to stand at 55xc2x0 C. and 80% RH for a period of 3 days, provided that the sensitivity is represented by the logarithm of reciprocal of exposure giving a density of 2.5 obtained when the photothermographic material is exposed and heat-developed at 117xc2x0 C. for 20 sec.;
13. The exposure method described in 12, wherein the photothermographic material is exposed to longitudinally multiple laser light;
14. The exposure method described in 13, wherein the laser light is not exposed at an angle substantially vertical to the exposed surface of the photothermographic material;
15. A photothermographic material comprising on a support, silver halide, an organic silver salt and a reducing agent. wherein the sensitivity of the photothermographic material meets the following requirement:
xe2x88x9215 less than 100xc3x97(S1-S0)/S0 less than 15
wherein S0 represents a sensitivity of the photothermographic material heat-developed after being allowed to stand at 23xc2x0 C. and 50% RH for a period of 3 days and S1 represents a sensitivity of the photothermographic material heat-developed after being allowed to stand at 55xc2x0 C. and 80% RH for a period of 3 days, provided that the sensitivity is represented by the logarithm of reciprocal of exposure giving a density of 2.5 obtained when the photothermographic material is exposed and heat-developed at 117xc2x0 C. for 20 sec.;
16. The photothermographic material described in 15, wherein a component layer of the organic salt containing side contains a contrast-increasing agent;
17. An image forming method comprising:
subjecting the photothermographic material described in 15. or 16. at a temperature of 105 to 145xc2x0 C.;
18. An image forming method comprising:
subjecting the photothermographic material described in 15. or 16. to exposure to longitudinally multiple laser light using an exposure apparatus; and
19. An image forming method comprising:
subjecting the photothermographic material described in 15. or 16. to exposure to laser light using an exposure apparatus,
wherein the angle between the laser light and the exposed surface of the photothermographic material is not substantially a right angle.